18x13/335 Square Under Stock Fenders

Discussion in 'GT350 and S550 Technical Forum' started by boardkat, Feb 26, 2018.

  1. boardkat

    boardkat CAMtard

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    .. and before anybody asks, no, there is not offset information contained within. Why? Well, ask yourself these questions - do you have:

    Front
    1.) Offset struts
    2.) "Right-sized" piston or enlarged strut hole
    3.) Camber plates
    4.) More than -3.5 camber
    5.) 700lbs+ 2.25ID 5" springs
    6.) A BIG-ASS adapter (and not having an aversion to running one)
    7.) Quik-Latch bumper attachment points
    8.) Rolled/Pulled/Spaced fenders
    9.) Fender liners removed
    10.) Creative placement of various parts/lines
    11.) Ability to stomach 2mm of inboard strut clearance and NO fender clearance with occasional rubbing/self-clearancing

    Rear
    1.) Rolled/Pulled fenders
    2.) Springs in the stock location (or inverted coilovers)
    3.) Inverted shocks
    4.) Relocated e-brake bracket/line and other creative movement of parts/lines
    5.) The "right" amount of -ve camber to meet your setup needs coupled with an offset that maximizes inboard/outboard clearance
    6.) Fender liners removed
    7.) Ability to stomach 2mm of inboard strut clearance and NO fender clearance with occasional rubbing/self-clearancing

    .. because if your answer to any of those questions is no, then the offset won't matter anyway. There is a LOT of work and compromises required to make this setup fit square under the stock fenders - not gonna lie. And it's taken ALL of those things mentioned to make it work. I've spent many hours over the years measuring, test fitting, moving, thinking and just plain staring at things. It's not for the faint of heart, and you can really make it a lot easier on yourself just cutting and flaring your fenders. But I street drive my car, and didn't want to do a plastic flare/rivet job on it, nor spend the Texa$$$ amount on doing it right with a stock-like cut/weld/paint application (I don't do metal/fab/paint), and I'm trying to minimize my front/rear track and overall width. So here we are :)

    OK, now that we've gotten THAT part taken care of, let's dive into the details! :D

    I've been running an 18x12/335 setup quite successfully for the past few seasons, but I'm always looking to maximize my grip in the pursuit of those precious tenths on the clock. I was able to reclaim some inboard room this off-season by doing a lot of testing/math to determine what actual amount of travel I'm using up front for the various spring rates I've run over the years. The end result was the conclusion that a 5" spring "should" give me "just enough", which, in turn, allowed me to relocate my perch back above my tire for my desired ride height for additional inboard clearance. The natural conclusion was, "Hey, now I can fit an 18x13 up there!", and the end result was this showing up at my front door after (4) months of waiting:

    [​IMG]

    13" from bead-to-bead but almost 14" overall width
    [​IMG]

    4yo for scale
    [​IMG]

    I tried to weigh them, but couldn't fit the damn things on my scale because they're too wide! I did weigh holding a wheel though, and it comes in at just under 25lbs - surprising, because they're basically the same weight as my 18x12 - biggest difference being the face (F14 vs. CF5), since the barrel on the F14 rev2 is the same as the CF5.

    So how much wider are we talking? Here's a comparison of my various setups:
    [​IMG]

    19x11 | 305/30R19 Michelin Pilot Sport 4S
    [​IMG]

    18x12 | 335/30R18 BFG Rival-S
    [​IMG]

    18x13 | 335/30R18 BFG Rival-S
    [​IMG]

    Ultimately, I've added an additional 0.75" of tire going from 12-13 on a 335, and the visual stretch of the sidewall (which was the desired outcome) should give me more sidewall support on a tire that tends to feel a little numb at the limit.

    So how does it fit? Let's take a look!

    Front, full droop:
    [​IMG]

    [​IMG]

    Front, maximum compression (fender limited):
    [​IMG]

    [​IMG]

    Here's how much shock travel is left right at the point of fender interference:
    [​IMG]

    While it looks like a lot of travel left on the table, I've actually never experienced compression travel this far on a 700lbs+ setup - and now with a 5" spring, I'll reach block height before I ever reach this point. But block height is also past the point of maximum compression achieved, so the end result is - 18x13/335 works up front! :D

    Apologies about the rear - I thought I took some pics, but apparently I didn't - suffice it to say that with some parts relocation, I moved almost all the additional width inboard, and used up what additional fender clearance I had left. Nothing on the table, it just barely fits, but with full compression travel without any fender or shock/frame interference! I'll remember to take some pics when I have the rear suspension apart in a few weeks putting in some final spring/alignment touches ahead of my California swing.

    Of course, the proof will be in the pudding - I've got my first event of the season next weekend. But with 40deg temps (and most likely rain) in the forecast (par for the course this time of year in the PNW), I probably won't get to test the new setup until the Fontana Pro Solo in late March. Not ideal to be testing at a national event a thousand miles away, but I'll make it work - or not, lol. Stay tuned!
     
    Fabman, RaiderJatt02, racer47 and 2 others like this.
  2. VoodooBoss

    VoodooBoss Rick Moderator

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    In for updates.
     
  3. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    Interesting :)
     
  4. boardkat

    boardkat CAMtard

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    Bolted all (4) on for the first time tonight and took a drive with a few hard corners and bumps. No rub!
    Sidenote: sticker BFG Rival S in cold (low-40s) and wet conditions don't grip so well. Tread carefully! o_O

    Apologies on the potato quality pics; my garage is a lot wider than it is long (and it should be pretty obvious why I spend so much time on my back, inconveniently placed support beams FTL!!), so taking pics is difficult, especially in the dark!
    [​IMG]

    Front:
    [​IMG]

    [​IMG]

    Rear:
    [​IMG]

    [​IMG]
     
    Last edited: Feb 27, 2018
    RaiderJatt02 and Grant 302 like this.
  5. Grant 302

    Grant 302 OPM Spent: $509,979 Moderator

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    I don't know why, but that's damn funny! :D

    Those are some big MEATS!
     
  6. ArizonaBOSS

    ArizonaBOSS Because racecar. Moderator

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    When do you get to test them out on-track/Autox?
     
  7. boardkat

    boardkat CAMtard

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    not this weekend - i'll probably be hitting the course on the 1st run with temps in the low-30s. uggh.
    one more chance to try it out in a few weeks on an airport course in a drier part of the state, fingers crossed. otherwise, i'll be hauling them down to fontana with me for the pro solo (3) weekends from now. they'll definitely be getting worked there :D
     
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  8. boardkat

    boardkat CAMtard

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    so i was wrong. i *did* get to test it out this weekend! weather was dry for once, albeit very chilly (sub-40deg). tires never really got to temp, but did put a good scrub on them, and validated that there is no rub/interference (on a very bumpy course, too).

    [​IMG]
     
  9. VoodooBoss

    VoodooBoss Rick Moderator

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    Nice work!
     
    boardkat likes this.
  10. 1Danapple8

    1Danapple8 TMO Intermediate

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    How difficult would it be to run a set of 11.5 squared with some of the modifications you have, I.E offset front strut, inverted shocks, and potentially the gt350 fenders. I dont like the way the 11.5 sticks out on the gt350r and id like to push it in slightly but im not sure if itl fit with coilovers in the rear, and as for the fronts id like to run a square setup with r888rs, however the tread width for the 305s is 11.5 inches. So id want to step up to an 11.5 as apposed to 11 square
     

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